An increased demand for more fuel efficient engines without compromising performance has led to the development of displacement on demand (DoD) internal combustion engines. DoD engines include a control system that deactivates cylinders under low load conditions and reactivates cylinders under high load conditions. For example, an eight cylinder engine can operate using four cylinders to improve fuel economy by reducing pumping losses but can use all eight cylinders when more power is required such as during acceleration. A DoD engine is in an activated mode when using all of the cylinders and a deactivated mode when using less than all of the cylinders.
In the deactivated mode, there are less cylinders operating. As a result, there is less drive torque available to drive the vehicle driveline and accessories (e.g., alternator, coolant pump, A/C compressor). Engine efficiency, however, is increased as a result of decreased fuel consumption (i.e., no fuel supplied to the deactivated cylinders) and decreased engine pumping. Because the deactivated cylinders do not take in fresh intake air, pumping losses are reduced.
A lifter oil manifold assembly (LOMA) is implemented to activate and deactivate select cylinders of the engine. The LOMA includes a series of solenoids associated with corresponding cylinders. The solenoids are selectively energized to enable hydraulic fluid flow to switchable lifters to inhibit valve operation, thereby deactivating the corresponding cylinders. In the event of a solenoid failure, mechanical damage may occur to the engine. Therefore, it is advantageous to detect a faulty solenoid quickly to prevent possible engine damage.
One method to detect a faulty solenoid is to monitor for an electrical short or an open circuit. However, this method will only detect an electrical failure of the solenoid without regard to a mechanical failure such as a stuck solenoid.